I would re-examine the power supply head room. Are you sure you have at least double the Watts the machine draws on average?
Then power down and gently push all drive connections and power to the drives home. Re-test.
If that doesn't help, remove spare drives and re-test.
Im using windows 7 to act as a software raid/striped drive for two 1.5 TB drives. A few months ago one of the drives stopped working but it kicked back in when the computer restarted. Now it seems one of the two drives are gone for good, or at least; It says the drive is missing. It still seems to show the drive in the disk manager, it lists it's total volume but it wont let me look at the properties. It shows the drive it's paired with(Listed as working properly in it's properties though listed as failed in the Drisk manager).
Are there any further measures I can take to diognose what is wrong with it and possibly re-enable this drive?